Blood or serum calcium levels may have diagnostic value and/or be valuable for treatment implications. The reference range for calcium ions is very narrow, 2.20 to 2.55 mmol/L, and slight deviations above or below these levels may be diagnostic of several physiological disorders. The two most common diseases associated with hypercalcaemia (elevated serum calcium) are hyperparathyroidism and malignancy, especially when the malignancy has metastasized to the skeleton and caused bone resorption (i.e. local destruction of the bone accompanied by release of calcium from the site of the metastatic lesion). Decreased serum calcium levels (hypocalcaemia) are commonly associated with hypoparathyroidism. About 1% of newborns have significant hypocalcaemia (serum calcium<1.75 mmol/L) with symptoms like irritability, twitching and convulsions which require immediate medical intervention.
Magnesium, like calcium, is a major element found in the body. Impairments in the level of magnesium also lead to clinical symptoms some of which are very similar to the ones found with impaired levels of calcium. Given the nearly identical clinical symptoms of low serum calcium and low serum magnesium, it can be imperative to delineate which element is causing the clinical symptoms. As such, often both serum calcium and magnesium measurements are necessary to determine which element or as the case may be whether both elements are out of normal range. Further, in some cases quantification of the magnesium may interfere with the quantification of calcium.
Currently, the reference method for measuring calcium and magnesium is atomic absorption. However, for routine measurements, atomic absorption is somewhat inconvenient, requiring expensive instrumentation and a rather skilled operator to perform the assays in order to achieve sufficient precision and reproducibility.